Help with JAVA Address Book Demo

Hello!
I'm trying to modify JAVA Address Book Demo from Using Java DB in Desktop Applications so the contacts will be saved in a text file and not using DB? I tried modifying this program but I didn't managed to save contacts in a txt file.

...okay, and what was the problem? What does that do? What would you expect it to do?

If you want help, you have to be specific. Post an SSCCE that demonstrates exactly what you're doing and the problem you're having. That doesn't mean post your whole project- boil it down to the bare minimum.